The long-term objective of the proposed research program is to develop a double-acting lever drive combined with an adjustable three-speed system for wheelchair propulsion. Improved mobility should encourage exercise and provide an opportunity to improve user physical fitness and, thus, contribute to a higher level of rehabilitation. Propulsion interface devices such as handrims, levers and cranks offer varying degrees of efficacy and efficiency in performance. Studies conducted at Wright State University and the University of Virginia support further development of devices which incorporate asynchronous operation and the use of three-speed hubs for gearing manually-propelled wheelchairs. The specific aims of the Phase I project are to a) develop a mechanism which simulates the proposed concept, and integrate it into an existing wheelchair; b) evaluate the mechanism's effect on the metabolic cardiovascular and pulmonary systems of the user; c) determine the marketability of the device, and; d) outline the program for further development and analysis in Phase II. It is anticipated that the device will be incorporated into commercially-manufactured wheelchairs and retrofitted to existing wheelchairs. The device also has application into other physical development equipment for disabled persons.